H3c O

An alternative way of making estradiol is based on using androstenolon acetate (3-acetoxy-5-androsten-17-one) (28.1.18). Reduction of the keto-group in this molecule by hydrogen using a Raney nickel catalyst and subsequent acylation of the resulting hydroxyl group with benzoyl chloride forms a diester (28.1.19). This undergoes a number of transformations, in particular reduction of the double bond at C5 - C6 with hydrogen over a platinum catalyst, and then mild alkaline hydrolysis in methanol of the acetyl protecting group at C3, oxidation of the resulting hydroxyl group to a ketone using chromium (VI) oxide, and then the benzoyl protecting group of the hydroxyl at C17 is hydrolyzed by an aqueous base, giving the keto-alcohol (28.1.20). This compound undergoes bromination with molecular bromine, just as in the method described for making estrone, which results in the formation of a dibromide (28.1.21). This product undergoes dehydrobromination when heated in collidine, giving a dienone (28.1.22). When heated in tetraline to a temperature about 325 °C, methane molecule cleaves off the position 10 followed by aromatization of the ring A, and the desired estradiol (28.1.17) is formed [25,26]. Estradiol is also made in other ways [27,28].

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